Cascade Sequence of Photooxygenation-Epoxidation for the Flow Synthesis of Epoxy Alcohols.

A photooxygenation-epoxidation cascade sequence converting alkenes to epoxy alcohols was developed and evaluated in batch and continuous-flow systems. In the batch system, the undesired interactions between the photooxygenation and epoxidation catalysts resulted in suboptimal yields, whereas the fine control of reaction parameters in the flow system allowed the allyl hydroperoxides produced through photooxygenation of alkenes to be rapidly converted to epoxy alcohols in yields of up to 93%. The developed procedure allows one to avoid an important synthetic bottleneck, works well where traditional batch synthesis fails, and can be scaled up to meet the needs of industrial production, thus presenting a valuable addition to the toolbox of practicing organic chemists.

Performance of NIR-Mediated Antibacterial Continuous Flow Microreactors Prepared by Mussel-Inspired Immobilization of Cs0.33WO3 Photothermal Agents.

An antibacterial continuous flow microreactor was successfully prepared by sequential mussel-inspired surface engineering of microchannels by using catechol-grafted poly(N-vinylpyrrolidone) and immobilization of near-infrared active Cs0.33WO3 nanoparticles inside the polydimethylsiloxane(PDMS)-based microreactors. Excellent phothothermal antibacterial acitivity over 99.9% was accomplished toward Gram-positive and -negative bacteria upon near-infrared irradiation during continuous operation up to 30 days. This was achieved without releasing Cs0.33WO3 nanoparticles from the surface of the microchannels, confirming the robust immobilization of photothermal agents through the mussel-inspired chemistry. The cleaning of used microreactors was easily attainable by simple acid treatment to release immobilized photothermal agents from the surface of the microchannels, enabling efficient recycling of used microreactors.

Rapid fluorescence detection of hypoxic microenvironments by nitro-benzyl conjugated chitosan nanoparticles encapsulating hydrophobic fluorophores.

In this study, hypoxia-responsive chitosan nanoparticles (HRCNs) were synthesized by the conjugation of nitro-benzyl derivatives into chitosan polymers and the subsequent self-assembly of them with hydrophobic fluorophores. The nitro-benzyl substrate of HRCNs could be selectively reduced by NTR/NADH that was overexpressed under hypoxic conditions, while it was not responsive to reductive agents (GSH or DTT) commonly existing in biological systems. The HRCN encapsulated with Rhodamine 6G (HRCN-R6G) was successfully applied for the rapid determination of the hypoxic status of lung carcinoma cells (A549) within 30 min, while several hours were required in a conventional assay. In the hypoxic microenvironment, the fluorescence intensity of HRCN-R6G was 2.6-fold higher than that in normoxic conditions. Taken together, the HRCN-R6G is expected to be used for the rapid diagnosis and treatment of hypoxia-related acute diseases, after the incorporation of therapeutic drugs into them.

Green diacetoxylation of alkenes in a microchemical system.

The palladium-catalyzed diacetoxylation and trifluoromethanesulfonic acid-catalyzed diacetoxylation using inexpensive and environmentally friendly hydrogen peroxide and peracetic acid were successfully conducted with the help of microchemical technology. Excellent yield and selectivity were achieved in significantly shortened reaction times without the decomposition of explosive oxidants and further transformation of unstable products, offering a safe and efficient alternative to traditional methods for alkene diacetoxylation.

High performance of a solid-state flexible asymmetric supercapacitor based on graphene films.

Solid-state flexible energy storage devices hold the key to realizing portable and flexible electronic devices. Achieving fully flexible energy storage devices requires that all of the essential components (i.e., electrodes, separator, and electrolyte) with specific electrochemical and interfacial properties are integrated into a single solid-state and mechanically flexible unit. In this study, we describe the fabrication of solid-state flexible asymmetric supercapacitors based on an ionic liquid functionalized-chemically modified graphene (IL-CMG) film (as the negative electrode) and a hydrous RuO(2)-IL-CMG composite film (as the positive electrode), separated with polyvinyl alcohol-H(2)SO(4) electrolyte. The highly ordered macroscopic layer structures of these films arising through direct flow self-assembly make them simultaneously excellent electrical conductors and mechanical supports, allowing them to serve as flexible electrodes and current collectors in supercapacitor devices. Our asymmetric supercapacitors have been optimized with a maximum cell voltage up to 1.8 V and deliver a high energy density (19.7 W h kg(-1)) and power density (6.8 kW g(-1)), higher than those of symmetric supercapacitors based on IL-CMG films. They can operate even under an extremely high rate of 10 A g(-1) with 79.4% retention of specific capacitance. Their superior flexibility and cycling stability are evident in their good performance stability over 2000 cycles under harsh mechanical conditions including twisted and bent states. These solid-state flexible asymmetric supercapacitors with their simple cell configuration could offer new design and fabrication opportunities for flexible energy storage devices that can combine high energy and power densities, high rate capability, and long-term cycling stability.

Triple-channel microreactor for biphasic gas-liquid reactions: Photosensitized oxygenations.

A triple-channel microreactor fabricated by means of a soft-lithography technique was devised for efficient biphasic gas-liquid reactions. The excellent performance of the microreactor was demonstrated by carrying out photosensitized oxygenations of α-terpinene, citronellol, and allyl alcohols.

Low pressure ethenolysis of renewable methyl oleate in a microchemical system.

A microchemical system for ethenolysis of renewable methyl oleate was developed, in which the dual-phase, microfluidic design enabled efficient diffusion of ethylene gas into liquid methyl oleate through an increased contact area. The increased mass transfer of ethylene favored the formation of desired commodity chemicals with significantly suppressed homometathesis when compared to the bulk system. In addition to higher selectivity and conversion, this system also provides the typical advantages of a microchemical system, including the possibility of convenient scale-up.

Efficient photosensitized oxygenations in phase contact enhanced microreactors.

A transparent dual-channel microreactor with highly enhanced contact area-to-volume ratio was fabricated for efficient photosensitized oxygenations. The dual-channel microreactor shielded with polyvinylsilazane (PVSZ) consisting of an upper channel for liquid flow and a lower channel for O(2) flow, allows sufficient phase contact along the parallel channels through a gas permeable PDMS membrane for maintaining the O(2) saturated solution. Under full exposure of reactants to light, the reactions in high concentration are completed in minutes rather than hours that it takes to complete in a batch reactor. Moreover, the scale-up process using the microreactor revealed higher productivity than the batch reactor, which would be valuable for the practical applications in a broad range of gas-liquid chemical reactions.

Dual-channel microreactor for gas-liquid syntheses.

A microreactor consisting of two microfluidic channels that are separated by a thin membrane is devised for intimate contact between gas and liquid phases. Gas flowing in one microchannel can diffuse into the liquid flowing in the other microchannel through the thin membrane. An oxidative Heck reaction carried out in the dual-channel (DC) microreactor, in which gaseous oxygen plays a key role in the catalytic reaction, shows the significant improvement that can be made over the traditional batch reactor and the conventional segmental microreactor in terms of yield, selectivity, and reaction time. It also allows independent control of the flow of the gaseous reagent. The proposed DC microreactor should prove to be a powerful tool for fully exploring gas-liquid microchemistry.

Efficient diacetoxylation of alkenes via Pd(II)/Pd(IV) process with peracetic acid and acetic anhydride.

A palladium-catalyzed diacetoxylation of alkenes in the presence of peracetic acid and acetic anhydride was developed to produce diacetates efficiently and diastereoselectively. Due to its mild conditions, this method was suitable for a broad range of substrates encompassing conjugated and nonconjugated olefins.

Formal aromatic C-H insertion for stereoselective isoquinolinone synthesis and studies on mechanistic insights into the C-C bond formation.

Formal aromatic C-H insertion of rhodium(II) carbenoid was intensively investigated to develop a new methodology and probe its mechanism. Contrasting with the previously proposed direct C-H insertion, the mechanism was revealed to be electrophilic aromatic substitution, which was supported by substituent effects on the aromatic ring and a secondary deuterium kinetic isotope effect. Various isoquinolinones were synthesized intramolecularly via six-membered ring formation with high regio- and diastereoselectivity, while averting the common Buchner-type reaction. Intermolecularly, dirhodium catalyzed formal aromatic C-H insertion on electron-rich aromatics was also achieved.

Efficient three-component Strecker reaction of aldehydes/ketones via NHC-amidate palladium(II) complex catalysis.

A simple and efficient one-pot, three-component method has been developed for the synthesis of alpha-aminonitriles. This Strecker reaction is applicable for aldehydes and ketones with aliphatic or aromatic amines and trimethylsilyl cyanide in the presence of a palladium Lewis acid catalyst in dichloromethane solvent at room temperature.

Air/Water-Stable Tridentate NHC-Pd Complex; Catalytic C-H Activation of Hydrocarbons via H/D Exchange Process in D(2)O.

While developing novel catalysts for carbon-carbon or carbon-heteroatom coupling (N, O, or F), we were able to introduce tridentate NHC-amidate-alkoxide palladium(II) complexes. In aqueous solution, these NHC-Pd(II) complexes showed high ability for C-H activation of various hydrocarbons (cyclohexane, cyclopentane, dimethyl ether, THF, acetone, and toluene) under mild conditions.

Asymmetric intermolecular heck-type reaction of acyclic alkenes via oxidative palladium(II) catalysis.

Herein, we report an asymmetric intermolecular Heck-type reaction of acyclic alkenes by using a palladium-pyridinyl oxazoline diacetate complex under oxidative palladium(II) catalysis conditions. A premade palladium-ligand complex afforded higher enantioselectivities than a corresponding premixed palladium-ligand system, while offering enhanced asymmetric induction when compared to known intermolecular Heck-type protocols.